Method and apparatus for depositing a silicon oxide film

ABSTRACT

In a film deposition process wherein a plasma generation chamber is divided from a deposition chamber, radicals are extracted from the plasma generation chamber to the deposition chamber and caused to react with a process gas to form a silicon oxide film. The deposition apparatus has a host controller for dictating a pattern of control of the process gas flow to an MFC provided in a feed part for feeding the process gas into the deposition chamber. The host controller gives the MFC instructions for executing control to, in a first half side time constituting not more than half of the whole film deposition time, first make zero or limit and then gradually increase the process gas flow. The process gas flow in the first half side time can also be limited so that the thickness of film deposited in the first half side time is not greater than 10% of the overall thickness of the silicon oxide film. A silicon-hydrogen compound (Si n H 2n+2 (n=1,2,3, . . . )) is used as the process gas.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method and an apparatus fordepositing a silicon oxide film. In particular, the invention isapplicable to a film deposition apparatus wherein a plasma generationchamber is divided from a deposition chamber, radicals are extractedfrom the plasma generation chamber to the deposition chamber, and a thinsilicon oxide film is deposited on a substrate by the radicals beingmade to react with a process gas including silicon atoms supplied to thedeposition chamber. In this deposition apparatus, the supply rate of theprocess gas in an initial stage after deposition is started, that is, ina first half side time constituting not more than half of the whole filmdeposition time, is limited.

[0003] 2. Description of the Related Art

[0004] There have been deposition apparatuses wherein a depositionchamber and a plasma generation chamber are spatially divided and thedeposition chamber and the plasma generation chamber each form aseparate space. The divided structure of the deposition chamber and theplasma generation chamber in this kind of deposition apparatus preventsthe plasma from making contact with the substrate. Only a gas for plasmageneration is fed to the plasma generation chamber, and there a plasmadischarge occurs under predetermined conditions and neutral activeradicals are created. A process gas for film deposition is fed to thedeposition chamber, and the above-mentioned radicals are also suppliedto the deposition chamber through multiple holes formed in a partitiondisposed between the deposition chamber and the plasma generationchamber. Film deposition on a substrate in the deposition chamber isbased on CVD (Chemical Vapor Deposition) resulting from a reactionbetween the radicals and the process gas. In the deposition of a siliconoxide film using this CVD method, a gas including silicon atoms is usedas the process gas. The process gas is mixed with the radicals in thedeposition chamber. As necessary, a carrier gas is also introduced. Theprocess gas including silicon atoms is for example a silicon-hydrogencompound.

[0005] In related art methods for depositing a silicon oxide film, theflow of the process gas fed to the deposition chamber has normally beenso controlled that from the start of plasma discharge to the end ofplasma discharge (i.e. for the whole film deposition time) the flow isheld to a required constant value determined by deposition conditions.Also, in the silicon oxide film deposition method discussed above, toraise the deposition rate to improve productivity and practicality, theflow of the process gas fed to the deposition chamber in the filmdeposition immediately following the start of plasma discharge has beenset to a relatively high value.

[0006] However, as another side to this, when the supply rate at whichthe process gas is supplied in the film deposition immediately followingthe start of plasma discharge is too great, a silicon oxide filmcontaining excess silicon is deposited. Silicon in the silicon oxidefilm produces an effect of carrier trap levels. Consequently, with asilicon oxide film including excess silicon, because a great manycarrier trap levels are formed in the film, its electricalcharacteristics are poor. And when a silicon oxide film including excesssilicon is used in a semiconductor device, the device characteristicsdeteriorate markedly.

[0007] Specifically, when a silicon oxide film including excess siliconis used as a gate insulating film of a TFT, the problem arises that theoperating characteristics of the TFT fluctuate.

[0008] Considering this problem, to make good the device characteristicsin the formation of the silicon oxide film, the flow of silicon atoms atthe time of the plasma discharge should be set to a low value. In fact,J. Batey et al. have proposed in an article of theirs that to improvethe electrical characteristics of a silicon oxide film it is effectiveto make the deposition rate of the silicon oxide film low (J. Appl.Phys. 60(9), Nov. 1, 1986). This article states as a conclusion that itis not possible to form a silicon oxide film having good electricalcharacteristics unless the film deposition rate is set to 0.13 nm/sec orless. However, because when the deposition rate is made 0.13 nm/sec orless like this the formation of the film takes time, from the point ofview of practicality it is difficult to adopt this low deposition rate.

SUMMARY OF THE INVENTION

[0009] It is therefore an object of the present invention to provide amethod and an apparatus with which it is possible to deposit a siliconoxide film having good electrical characteristics and which areeffective from the practical application point of view.

[0010] A silicon oxide film deposition method provided by the inventionis a method for forming a silicon oxide film on a substrate bygenerating a plasma in a plasma generation chamber divided from adeposition chamber, extracting radicals in the plasma from the plasmageneration chamber to the deposition chamber, and causing these radicalsto react in the deposition chamber with a process gas including siliconatoms fed to the deposition chamber. In this film deposition method, thesupply rate of the process gas is, in a first half side timeconstituting not more than half of the whole film deposition time, firstlimited to zero or another desirably low supply rate and then controlledto gradually increase. The process gas supply rate in the first halfside time can also be limited so that the thickness of film formed bythe deposition in the first half side time is not greater than 10% ofthe overall thickness of the silicon oxide film.

[0011] In this method for depositing a silicon oxide film, asilicon-hydrogen compound (Si_(n)H_(2n+2)(n=1,2,3, . . . )) ispreferably used as the process gas. An inert gas (a noble gas such asAr) can also be introduced as a diluting gas along with thesilicon-hydrogen compound process gas. In this case, the mixtureproportions of the process gas and the inert gas can be determinedfreely.

[0012] And in this method for depositing a silicon oxide film, as thepattern of control of the increase of the process gas supply rate,preferably the increase is controlled in correspondence with time or iscontrolled on the basis of any of a linear function, a second-orderfunction, an exponential function or a step function.

[0013] The rate at which the silicon oxide film is deposited in thefirst half side time constituting not more than half of the whole filmdeposition time is preferably not greater than 0.13 nm/sec.

[0014] As the gas for producing the radicals, any gas from among O₂, O₃,N₂O, CO, CO₂ and nitrogen oxide gases is used.

[0015] In a silicon oxide film deposition apparatus according to theinvention, radicals are extracted to a deposition chamber from a plasmageneration chamber divided from the deposition chamber, and in thedeposition chamber the radicals are caused to react with a process gasincluding silicon atoms to deposit a silicon oxide film on a substrate.A feed part for feeding the process gas to the deposition chamber isprovided between a process gas supply and the deposition chamber, and amass flow controller (MFC) is provided in the feed part. The mass flowcontroller regulates the flow of the process gas supplied to thedeposition chamber. A value determining the flow of the process gas isset in the mass flow controller. A host controller for issuinginstructions to the mass flow controller dictating this set valuedetermining the flow of the process gas is also provided. This hostcontroller controls the process gas supply device rate by way of themass flow controller. That is, the host controller, in a first half sidetime constituting not more than half of the whole film deposition time,first sets to zero or limits the process gas supply rate and thengradually increases it. The host controller may also limit the processgas supply rate in the first half side time so that the thickness offilm deposited in the first half side time is not greater than 10% ofthe overall thickness of the silicon oxide film.

[0016] In this deposition apparatus, a silicon-hydrogen compound(Si_(n)H_(2n+2)(n=1,2,3, . . . )) is preferably used as the process gas.An inert gas (a noble gas such as Ar) can also be introduced as adiluting gas along with the silicon-hydrogen compound process gas. Inthis case, the mixture proportions of the process gas and the inert gasare freely determinable.

[0017] According to the invention, the feed rate of the process gas usedfor the deposition of the silicon oxide film is limited in a first halfside time constituting not more than half of the whole film depositiontime. The partial pressure of SiH₄ or the like in the deposition chamberis lowered in the first half side time constituting not more than halfof the whole film deposition time, and as a result the deposition rateof the silicon oxide film is suppressed and a state of excess silicon inthe silicon oxide film is prevented. When a state of excess silicon isprevented, carrier trap levels in the silicon oxide film are reduced,and the film quality is improved. Also in the first half side timeconstituting not more than half of the whole film deposition time, theflow of the process gas is gradually increased on the basis of any ofvarious patterns of control. By this means the deposition rate isincreased, the overall time required for film deposition is shortened,the productivity of the film is raised, and the practicality of thedeposition method or the deposition apparatus is raised. The supply rateof the process gas including silicon atoms is only limited for aninitial period immediately following the start of plasma discharge, andthereafter the process gas supply rate is increased in any of variouspatterns of variation. When the formation of regions of SiO containingexcess silicon in the silicon oxide film is prevented, the number ofcarrier trap levels is reduced, leak current is reduced and theelectrical characteristics of the film are improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a block diagram showing the construction of a siliconoxide film deposition apparatus according to the invention;

[0019]FIG. 2 is a graph showing a first preferred embodiment of apattern of variation of a process gas supply rate according to theinvention;

[0020]FIG. 3 is a graph showing a second preferred embodiment of apattern of variation of a process gas supply rate according to theinvention;

[0021]FIG. 4 is a graph showing a third preferred embodiment of apattern of variation of a process gas supply rate according to theinvention;

[0022]FIG. 5 is a graph showing a relationship between process gassupply rate and deposition rate pertaining to the invention;

[0023]FIG. 6 is a graph illustrating a reduction in carrier trap levels;

[0024]FIG. 7 is a graph showing variations of partial pressure in anSiH₄ supply method of related art;

[0025]FIG. 8 is a graph showing variations of partial pressure in anSiH₄ supply method according to the invention; and

[0026]FIG. 9 is a graph showing an example of a specific construction ofa deposition apparatus used in the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Preferred embodiments of the invention will now be described withreference to the accompanying drawings. The preferred embodimentsdescribed here are examples of specific realizations of the invention,and the technological scope of the invention is not limited to thesepreferred embodiments.

[0028] Referring to FIG. 1, a film deposition apparatus 11 has a plasmageneration chamber 11 a and a deposition chamber 11 b spatially dividedfrom each other. A structure for separating the plasma generationchamber 11 a and the deposition chamber 11 b is provided between thetwo. For example a partition 11 c with numerous through holes formed init is provided between the plasma generation chamber 11 a and thedeposition chamber 11 b. The internal spaces of the plasma generationchamber 11 a and the internal space of the deposition chamber 11 b areconnected by the numerous through holes in the partition 11 c.

[0029] A gas for plasma generation is introduced into the plasmageneration chamber 11 a. The gas used for plasma generation is forexample anyone from among O₂, O₃, N₂O, CO, CO₂ and nitrogen oxide gasesor is a mixed gas made by suitably mixing two or more of these gases.When the gas for plasma generation is introduced into the plasmageneration chamber 11 a and for example radio frequency (RF) power froman RF generator (not shown) is also supplied, an electrical discharge isinduced and a plasma is generated. When the plasma is generated, neutralactive radicals are created in the plasma. Because the above-mentionedpartition 11 c is provided between the plasma generation chamber and thedeposition chamber, charged particles in the plasma are not supplied tothe deposition chamber 11 b. The partition 11 c allows only the radicalsto pass through its through holes into the deposition chamber 11 b.

[0030] A process gas (or source gas) for film deposition is introducedinto the deposition chamber 11 b. The process gas is introduced onlyinto the inside of the deposition chamber 11 b. In the structure of thefilm deposition apparatus 11, the deposition chamber 11 b and the plasmageneration chamber 11 a are separated by the partition 11 c, and by thismeans the process gas is prevented from coming into contact with theplasma. For example, a process gas feed mechanism is built into theinterior of the partition 11 c. The process gas is fed into thedeposition chamber 11 b through the process gas feed mechanism. Theprocess gas feed mechanism is for example made up of a reservoir spacefor holding the process gas and numerous diffusion holes provided in thedeposition chamber 11 b.

[0031] Here, with reference to FIG. 9, a specific example of aconstruction of the film deposition apparatus 11 will be described.

[0032] This film deposition apparatus 11 is a CVD reactor. In the filmdeposition apparatus 11, silane is used as a process gas to deposit asilicon oxide film as a gate insulating film on the upper face of aglass substrate 111 for a TFT. When deposition is carried out, theinside of a vessel 112 of the film deposition apparatus 11 is kept in adesired vacuum state by an evacuating mechanism 113. The evacuatingmechanism 113 is connected to an exhaust port 112 b-1 formed in thevessel 112.

[0033] A horizontal partition 114 (equivalent to the partition 11 cmentioned above) made from an electrically conducting material isprovided inside the vessel 112. The partition 114 is circular and ismounted with its periphery pressed upon by the underside of an annularinsulating member 122 so as to form a seal. The inside of the vessel 112is divided by the partition 114 into two chambers, an upper chamber anda lower chamber. The upper chamber is a plasma generation chamber 115and the lower chamber is a deposition chamber 116. The partition 114 hasa predetermined thickness and as a whole has the form of a flat plate.An internal space 124 is formed in the partition 114.

[0034] The glass substrate 111 is disposed on a substrate holdingmechanism 117 provided in the deposition chamber 116. The potential ofthe substrate holding mechanism 117 is kept at a ground potential, whichis the same potential as the vessel 112. Also, a heater 118 is providedinside the substrate holding mechanism 117.

[0035] The vessel 112 is made up of an upper vessel 112 a forming theplasma generation chamber 115 and a lower vessel 112 b forming thedeposition chamber 116. When the upper vessel 112 a and the lower vessel112 b are joined together to make the vessel 112, the partition 114 isinstalled between the two. The periphery of the partition 14 is mountedso as to make contact with the insulating member 122, which is the lowerof two annular insulating members 121, 122 interposed between thepartition 114 and the upper vessel 112 a when an electrode 120 isinstalled. By this means, the plasma generation chamber 115 and thedeposition chamber 116 are formed separated from each other on the upperside and the lower side of the partition 114. Plasma 119 is generated inthe plasma generation chamber 115. Multiple holes 120 a are formed inthe electrode 120. The partition 114 and the electrode 120 are supportedby the two annular insulating members 121, 122 provided around the innerface of the side of the upper vessel 112 a. Feed pipes 123 forintroducing oxygen gas to the plasma generation chamber 115 from outsideare provided in the annular insulating member 121. The feed pipes 123are connected to an oxygen gas supply source (not shown) via a mass flowcontroller (not shown) for performing flow control.

[0036] Although the inside of the vessel 112 is divided by the partition114 into the plasma generation chamber 115 and the deposition chamber116, multiple through holes 125 are formed dispersed in the partition114, passing through the internal space 124, and only by way of thesethrough holes 125 the plasma generation chamber 115 and the depositionchamber 116 are connected. The internal space 124 of the partition 114is a space for distributing the process gas and supplying it uniformlyto the deposition chamber 116. Multiple dispersion holes 126 forsupplying the process gas to the deposition chamber 116 are formed in alower wall of the partition 114. Feed pipes 128 for introducing theprocess gas are connected to the internal space 124. The feed pipes 128are disposed so as to be connected from the side. A baffle plate 127perforated with multiple holes 127 a so that the process gas is supplieduniformly through the dispersion holes 126 is provided inside theinternal space 124. The process gas fed into the internal space 124 bythe feed pipe 128 enters on the upper side of the baffle plate 127 andpasses through the holes 127 a of the baffle plate 127 into a space 124b on the lower side, and then passes through the dispersion holes 126and is dispersed into the deposition chamber 116. An electrode 129covered on its outside by an insulator 131 is connected to the electrode120 and supplies RF power thereto.

[0037] Returning to FIG. 1, the rest of the film deposition apparatus 11will now be described. In FIG. 1, the reference numeral 12 denotes anapparatus for supplying the process gas for film deposition. Process gassupplied from this process gas supply 12 passes through a gas feed line13 including an MFC (Mass Flow Controller) 13 a and is fed into theabove-mentioned process gas feed mechanism inside the partition 11 c. Asthe process gas, a silicon-hydrogen compound (Si_(n)H_(2n+2) (n=1,2,3, .. . )) such as SiH₄ is used. In the deposition chamber 11 b, the processgas introduced through the process gas feed mechanism inside thepartition 11 c reacts with the radicals introduced via the numerousthrough holes formed in the partition 11 c, the process gas is brokendown, and a silicon oxide film is deposited on a substrate placed in thedeposition chamber 11 b. In this way, a film is formed on the substrate.Preferably, along with the introduction of the process gas, an inert gas(a noble gas such as Ar) is introduced as a diluting gas. The mixtureproportions of the process gas and the inert gas are freelydeterminable.

[0038] The above-mentioned MFC 13 a has the function of regulating theflow of the process gas through the gas feed line 13. An MFC isessentially a flow control device for supplying a process gasautomatically. In this preferred embodiment, on the basis of commandsfrom a host controller, which will be discussed next, the flow of theprocess gas is regulated to vary the supply rate. In the MFC 13 a a setvalue for governing the flow of the process gas is set, and the flow ofthe process gas is controlled by this set value being varied with time.

[0039] As mentioned above, the host controller 14 feeds to the MFC 13 aprovided in the gas feed line 13, for example via communication means,commands dictating the pattern of the regulation of the flow of theprocess gas effected by the MFC 13 a. The host controller 14 therebycontrols the flow of process gas supplied to the deposition chamber 11 bthrough the MFC 13 a. By this means, the supply of process gas fed tothe deposition chamber 11 b can be controlled by the host controller 14to a desired value, as will be further discussed later.

[0040] It is also possible to provide the MFC itself with a controlfunction for executing the film deposition method of the invention, andto dispense with the host controller. However, as will be furtherdiscussed later, because the pattern of the variation of the flow ofprocess gas supplied to the deposition chamber 11 b may be subtle andcomplex, it is preferable for a host controller with a high capabilityto be provided. When considering an actual design, it is possible toselect freely the location of the control means for working a filmdeposition method, that is, method for supplying process gas, accordingto the invention.

[0041] In the graph 15 shown in FIG. 1, the horizontal axis shows time(t) and the vertical axis shows flow of process gas (sccm), and anexample 15 a of a variation of process gas flow is shown. In thispreferred embodiment, the pattern of the regulation of the process gasflow is controlled on the basis of commands from the host controller 14.That is, specifically, in a first half side time constituting not morethan half of the whole film deposition time, the supply rate (flow) ofprocess gas is first set to zero or is limited and then it is graduallyincreased, so that the supply rate of process gas in the first half sidetime as a whole is limited.

[0042] Next, various methods for the pattern of control of the flow,that is, the supply rate, of the process gas will be described, as firstthrough fourth preferred embodiments.

[0043] First Preferred Embodiment:

[0044]FIG. 2 shows a representative example of control of the supplyrate of the process gas SiH₄. In the graph of FIG. 2 the horizontal axisshows time and the vertical axis shows feed flow. Times t₀, t₁, t₂,t_(e) are set on the time axis. For example oxygen (O₂) is used as theplasma generation gas. Time t₀ is the time at which the oxygen gas isfed into the plasma generation chamber and plasma discharge of theoxygen gas is started, and is the start time of film deposition. At timet₁, the supply of SiH₄ is started. Accordingly, from time t₀ to time t₁,supply of SiH₄ is not carried out, and the flow of the process gas atthis initial stage is zero. The supply of SiH₄ at this initial stage canalternatively be limited to another flow other than zero flow. Afterthat, between times t₁ and t₂, the supply rate of SiH₄ is graduallyincreased with time, and at time t₂ the supply rate of SiH₄ reaches aconstant value. The supply rate of SiH₄ from time t₂ to time t_(e), atwhich film deposition and plasma discharge end, is kept to this constantvalue.

[0045] By the process gas supply rate in an initial stage afterdeposition is started being made zero flow or being limited like this,the formation of a silicon oxide film having excess silicon at the startof deposition can be suppressed, and by the process gas supply ratebeing gradually increased from time t₁ to time t₂ thereafter, the filmdeposition time is shortened and practicality is raised. Thus, becausethe process gas supply rate is first limited and then graduallyincreased in the time t₀ to t₂ like this, the process gas supply rate asa whole is limited. The time t₀ to t₂ satisfies the relationship withrespect to the overall deposition time t₀ to t_(e) that(t₂−t₀)/(t_(e)−t₀)≦0.5. On the basis of this relationship, the time t₀to t₂ is defined as “a first half side time constituting not more thanhalf of the whole film deposition time”. In this first half side timeconstituting not more than half of the whole film deposition time, theprocess gas supply rate is so limited that the thickness of siliconoxide film formed in the first half side time is not greater than 10% ofthe overall thickness of the silicon oxide film.

[0046] Second Preferred Embodiment:

[0047]FIG. 3 shows another example of control of the supply rate of theprocess gas SiH₄. The times t₀, t₁, t₂ on the time axis have the samesignificance as described above. In this example, control is carried outso that the supply rate from t₁ to t₂ is increased according to a stepfunction. In this example also, in a first half side time constitutingnot more than half of the whole film deposition time, by the process gassupply rate first being made zero flow or being limited, the formationof a silicon oxide film having excess silicon is suppressed, and also bythe process gas supply rate then being gradually increased according toa step function the film deposition time is shortened and practicalityis raised.

[0048] Third Preferred Embodiment:

[0049]FIG. 4 shows other examples of control of the supply rate of theprocess gas SiH₄. The times t₀, t₁, t₂ on the time axis have the samesignificance as described above. In this example, control is carried outso that the supply rate from t₁ to t₂ is increased according to any ofvarious functions, for example a proportional, linear function, asecond-order function, or an exponential function. In this example also,in a first half side time constituting not more than half of the wholefilm deposition time, by the process gas supply rate first being madezero flow or being limited the formation of a silicon oxide film havingexcess silicon is suppressed, and also by the process gas supply ratethen being increased according to any of various functions the filmdeposition time is shortened and practicality is raised.

[0050] Fourth Preferred Embodiment:

[0051]FIG. 5 shows a preferable condition for increasing the supply rateof the process gas SiH₄. In FIG. 5 the horizontal axis shows supply rate(sccm) of SiH₄ and the vertical axis shows film deposition rate of SiO₂(nm/sec). After film deposition is started the supply of SiH₄ is startedat time t₁ and the SiH₄ supply rate is gradually increased, as shown inFIGS. 2 through 4, but at this time the SiH₄ supply rate is suppressedso that the deposition rate of the film formed on the substrate is notgreater than 0.13 nm/sec, as shown in FIG. 5. In this case, the O₂plasma generation conditions, the internal pressure where the substrateis placed and the electrode spacing have all been kept constant. Whenthis is done, when as shown in FIG. 6 the field strength vs. leakcurrent characteristic 21 of a silicon oxide film made by a method andapparatus not according to the present invention and the field strengthvs. leak current characteristic 22 of a silicon oxide film made inaccordance with the invention are compared, the leak currentcontribution 23 of carrier trap levels is reduced and carrier traplevels in the silicon oxide film are cut down and the above-mentionedeffects are still better obtained.

[0052] Next, with reference to FIG. 7 and FIG. 8, a method for supplyingthe process gas SiH₄ in the first half side time constituting not morethan half of the whole film deposition time described in the foregoingpreferred embodiments will be explained from the point of view ofpartial pressure changes. FIG. 8 shows partial pressures in the SiH₄supply method according to the invention. And for contrast, the partialpressure changes in a supply of SiH₄ according to a related art methodare shown in FIG. 7. In FIG. 7 and FIG. 8, the horizontal axis showstime and the vertical axis shows partial pressure inside the depositionchamber.

[0053]FIG. 7 shows a partial pressure characteristic 31 of SiH₄ and apartial pressure characteristic 32 of O₂. In the partial pressurecharacteristic 31, before t₀, which is the plasma discharge start time,and after t₃, which is a steady state arrival time, the partial pressureof SiH₄ is constant, and between t₀ and t₃ the partial pressure falls.The constant partial pressure before t₀ is a result of the supply andexhausting of SiH₄ being in equilibrium, and the constant partialpressure after t₃ is a result of the supply and consumption (exhaustingand deposition) of SiH₄ being in equilibrium. In the plasma dischargeperiod after t₀ the exhaust rate is constant and the supply of SiH₄ isalso constant, and consequently, compared with the period after t₃, SiH₄is consumed by the amount of the fall in partial pressure, and thisconsumed amount apparently all contributes to film deposition.

[0054] Thus in the period from the discharge start time t₀ to the steadystate arrival time t₃ (the time for which the discharge is in atransient state) the partial pressure of SiH₄ (or other process gasincluding Si) falls, this fall makes a film rich in Si, and in thesilicon oxide film a layer including too much silicon is formed in theinitial stage after deposition is started.

[0055]FIG. 8 also shows a partial pressure characteristic 41 of SiH₄ anda partial pressure characteristic 42 of O₂. In contrast with the relatedart supply method described above, in the partial pressurecharacteristic 41, the partial pressure of SiH₄ is kept substantiallyzero at the discharge start time t₀, and supply of SiH₄ is carried outand its partial pressure gradually raised from a certain time t₁ afterthe discharge start (t₀). The feed rate of SiH₄ after the supply isstarted at time t₁ is gradually increased in any of various patterns, asdescribed above, until time t₂ (=t₃), at which a steady state isreached.

[0056] By making the partial pressure of SiH₄ zero at the start ofplasma discharge like this, excessive consumption of SiH₄ is prevented.With a SiH₄ supply method according to the invention, the SiH₄ supplyrate in a first half side time constituting not more than half of thewhole film deposition time is limited, and the partial pressure of SiH₄is kept low from the start. By this means, the formation of a layerincluding excessive silicon in the silicon oxide film in the initialstage of deposition is prevented. The partial pressure characteristic32, 42 of O₂ rises between the discharge start time and the time atwhich a steady state is reached.

What is claimed is:
 1. A method for depositing a silicon oxide film in adeposition chamber divided from a plasma generation chamber, comprising:a process gas supply step of supplying to said deposition chamber aprocess gas including silicon atoms; a step of extracting radicals fromsaid plasma generation chamber to said deposition chamber; and a step ofdepositing a silicon oxide film on a substrate by causing said processgas and said radicals to react, wherein in said process gas supplyingstep the supply rate at which said process gas is supplied is, in afirst half side time constituting not more than half of whole filmdeposition time, first made zero or limited and then graduallyincreased.
 2. A method for depositing a silicon oxide film according toclaim 1, wherein the process gas supply rate in said first half sidetime is limited so that the thickness of film deposited in said firsthalf side time is not greater than 10% of the overall thickness of saidsilicon oxide film.
 3. A method for depositing a silicon oxide filmaccording to claim 1, wherein a silicon-hydrogen compound(Si_(n)H_(2n+2)(n=1,2,3, . . . )) is used as said process gas.
 4. Amethod for depositing a silicon oxide film according to claim 3, whereinan inert gas is introduced as a diluting gas along with saidsilicon-hydrogen compound process gas.
 5. A method for depositing asilicon oxide film according to any one of claims 1 through 4, whereinthe rate of increase of said process gas supply rate is controlled withrespect to time.
 6. A method for depositing a silicon oxide filmaccording to any one of claims 1 through 4, wherein the rate of increaseof said process gas supply rate is controlled in correspondence with alinear function.
 7. A method for depositing a silicon oxide filmaccording to any one of claims 1 through 4, wherein the rate of increaseof said process gas supply rate is controlled in correspondence with asecond-order function.
 8. A method for depositing a silicon oxide filmaccording to any one of claims 1 through 4, wherein the rate of increaseof said process gas supply rate is controlled in correspondence with anexponential function.
 9. A method for depositing a silicon oxide filmaccording to any one of claims 1 through 4, wherein the rate of increaseof said process gas supply rate is controlled in correspondence with astep function .
 10. A method for depositing a silicon oxide filmaccording to claim 1, wherein the deposition rate of the silicon oxidefilm in said first half side time constituting not more than half of thewhole film deposition time is not greater than 0.13 nm/sec.
 11. A methodfor depositing a silicon oxide film according to claim 1, wherein anygas from among O₂, O₃, N₂O, CO, CO₂ and nitrogen oxide gases is used asa gas for making said radicals.
 12. An apparatus for depositing asilicon oxide film, having a structure wherein a plasma generationchamber is divided from a deposition chamber, constructed to deposit asilicon oxide film on a substrate by extracting radicals from saidplasma generation chamber to said deposition chamber and causing saidradicals and a process gas including silicon atoms supplied to saiddeposition chamber to react, comprising: a feed part provided betweensaid deposition chamber and a process gas supply apparatus for feedingsaid process gas to said deposition chamber; a controller provided inthe feed part for regulating the flow of said process gas; and a hostcontroller for dictating to said controller the pattern of theregulation of said process gas flow, wherein said host controllercommands said controller to, in a first half side time constituting notmore than half of whole film deposition time, first make zero or limitand then gradually increase said the process gas flow.
 13. An apparatusfor depositing a silicon oxide film according to claim 12, wherein saidhost controller issues commands to said controller limiting said processgas flow in said first half side time so that the thickness of filmdeposited in said first half side time is not greater than 10% of theoverall thickness of the silicon oxide film.
 14. An apparatus fordepositing a silicon oxide film according to claim 12 or 13, wherein asilicon-hydrogen compound (Si_(n)H_(2n+2)(n=1,2,3, . . . )) is used assaid process gas.
 15. An apparatus for depositing a silicon oxide filmaccording to claim 14, wherein an inert gas is introduced as a dilutinggas along with said silicon-hydrogen compound process gas.